Molded workpieces of any three-dimensional form, including polyolefin-based moldings, fibers and films, are used on a very wide scale in practice. An important problem area here is improving the surface properties of these structurally nonpolar hydrocarbon components. Thus, the poor adhesion of coatings and adhesives is a central problem which has remained unsolved for decades despite numerous attempts to find a solution.
It is known from the prior art that the compatibility of plastic surfaces with coatings and adhesives can be improved, for example, by oxidative aftertreatment processes, such as corona or plasma treatment. In processes such as these, the surface of the plastic is oxidized or chemically modified in the presence of gases and discharges, so that certain surface properties of the plastic can be modified. However, apart from their high energy consumption, processes such as these always involve an additional step and lead to ozone emissions in the manufacture of plastic parts. In addition, chemical pretreatment processes, including for example treatment with fluorine or chlorine gas, with chromosulfuric acid or fluorosulfonic acid, etc., have also been known for some time.
EP-B-372 890 describes polyolefin- or polyester-based fibers with a lubricant adhesively applied to their surface. This lubricant comprises a mixture of (1) fatty acid diethanolamide, (2) a polyether-modified silicone, (3) a sorbitan fatty acid ester and (4) a metal salt of an alkyl sulfonate. Components (1) to (4) are present in special quantity ratios. According to page 3, lines 20 to 26, the mixture of components (1) to (4) is applied to the surface. The technique by which the mixture containing the four components is applied to the surface of fibers is described in detail on page 4, lines 6 to 9. The application techniques mentioned include a) the use of rollers, b) spraying and c) immersion. Accordingly, the process according to EP-B-372 890 is a process in which a mixture of components (1) to (4) is applied to the surface of polyolefin moldings in an additional process step. Accordingly, the expression xe2x80x9cadhesively applied to the fiber surfacexe2x80x9d used in claim 1 of EP-B-372 890 may be clearly interpreted by the expert to mean that any adhesion involved is loose and temporary, for example in the form of relatively weak adhesion forces, and cannot in any way to be considered to represent permanent anchorage.
In view of the very widely used traditional chemical aftertreatment processes, such as corona and plasma treatment, it is known to the expert that no exact statements can be made as to the various processes involved. However, it has been established that oxidative surface changes occur and result in the formation of certain xe2x80x9cactive centersxe2x80x9d. Unfortunately, their concentration generally decreases with time so that the pretreatment effect also is only in evidence for a certain time, generally not more than 72 hours (cf. for example, Klaus Stoeckert (Editor), xe2x80x9cVeredeln von Kunststoff-Oberflxc3xa4chenxe2x80x9d, Munich 1974, page 137).
One feature common to all the known processes is that, in general, the desired surface effects are only temporarily present.
EP-B-616 622 relates to extrudable compostable polymer compositions comprising an extrudable thermoplastic polymer, copolymer or mixtures thereof containing a degradation-promoting system of an auto-oxidative component and a transition metal. The auto-oxidative system comprises a fatty acid, a substituted fatty acid or derivatives or mixtures thereof, the fatty acid having 10 to 22 carbon atoms and containing at least 0.1% by weight of unsaturated compounds and at least 0.1% by weight of free acid. The transition metal is present in the composition in the form of a salt in a quantity of 5 to 500 ppm and is selected from the group consisting of cobalt, manganese, copper, cerium, vanadium and iron. In the form of a film around 100 microns thick, the composition is said to be oxidatively degradable to a brittle material over a period of 14 days at 60xc2x0 C. and at a relative air humidity of at least 80%.
WO 97/12694 and WO 98/42776 describe the use of amphiphiles for permanently improving the adhesive and/or coating compatibility of polyolefin-based moldings, fibers and films in which a mixture containing (a) predominantly one or more polyolefins, (b) one or more migratable amphiphiles and (c) of one or more transition metal compounds is subjected in the usual way to molding, for example by extrusion, at temperatures in the range from 180 to 320xc2x0 C. It is disclosed that dialkanolamides of unsaturated fatty acids, for example oleic acid diethanolamide or linoleic acid diethanolamide, are particularly suitable for use as component (b). So far as the nature of component (c) is concerned, WO 97/12694 makes particular mention of Co, Zr, Fe, Pb, Mn, Ni, Cr, V and Ce while WO 98/42776 refers in particular to Ti and Sn as the transition metal present in that component.
The present invention relates, in general, to methods of permanently improving the adhesive and/or coating compatibility of polyolefin-based moldings, fibers and films with the use of fatty acid amides.
The problem addressed by the present invention was to provide auxiliaries with which the adhesive and/or coating compatibility of polyolefin-based moldings, fibers and films could be lastingly and permanently improved. In other words, the object of the invention was to provide auxiliaries for permanently improving the affinity of polyolefin surfaces for adhesives and/or coatings. More particularly, the object of invention was to make it possible to establish high-strength bonds which would rule out unwanted adhesive failures and would ensure that the adhesive joint could only be destroyed by cohesive failure or by combined cohesive/adhesive failure. In particular, the effectiveness of the amphiphiles known from the prior art in permanently improving the adhesive and/or coating compatibility of polyolefin-based moldings, fibers and films would be quantitatively improved.
The present invention relates to the use of fatty acid amides for permanently improving the adhesive and/or coating compatibility of polyolefin-based moldings, fibers and films, a mixture containing
a) predominantly one or more polyolefins,
b) 0.01 to 20% by weightxe2x80x94based on the polyolefinsxe2x80x94of one or more fatty acid amides and
c) 0.01 to 1000 ppm of one or more transition metal compoundsxe2x80x94metal content of the transition metal compounds, based on the polyolefinsxe2x80x94being subjected in known manner to molding by extrusion, calendering, injection molding, blow molding and the like at temperatures of 180 to 330xc2x0 C., with the proviso that the fatty acid amides b) are selected from the class of compounds corresponding to general formula (I): 
in which R1 is a saturated alkyl group containing 5 to 21 carbon atoms, R2 and R3 independently of one another are hydrogen or alkyl groups containing 1 to 18 carbon atoms which may each be substituted by up to 6 OH groups, NH2 groups or C1-10 alkyl groups and in which up to three ethylene groups which are not immediately adjacent one another may be replaced by oxygen, with the proviso that R1 and R2 cannot both be hydrogen and the additional proviso that the mixture containing components a), b) and c) contains fatty acid amides based on unsaturated fatty acids at most in a quantity which corresponds to 40% by weight, based on the quantity of fatty acid amides b) based on saturated fatty acids.
xe2x80x9cTransition metalsxe2x80x9d in the context of the present invention are any transition metals in the narrower sense (cf. for example Rxc3x6mpps Chemie-Lexikon, Stuttgart 1977, pp. 3717) and, in addition, the metals tin (Sn) and lead (Pb).
The fatty acid amides b) of general formula (I) to be used in accordance with the invention are derived from C6-22 fatty acids. These fatty acids are characterized by the general formula (II) R1xe2x80x94COOH, in which R1 is as defined above.
In one embodiment, the fatty acid amides b) are fatty acid alkanolamides or dialkanolamides, the fatty acid on which these compounds are based being saturated C6-22 fatty acids.
The fatty acid alkanolamides are compounds corresponding to general formula (Ia): 
in which R1 is as defined above and R2 is a C1-18 alkyl group that may be substituted by up to 6 OH groups, NH2 groups or C1-10 alkyl groups. R2 is preferably a C1-6 alkyl group substituted by an OH group.
The fatty acid dialkanolamides are compounds corresponding to general formula (Ib): 
in which R1 is as defined above and R2 and R3 independently of one another are C1-18 alkyl groups that may be substituted by up to 6 OH groups, NH2 groups or C1-10 alkyl groups. R2 and R3 are preferably C1-6 alkyl groups substituted by an OH group.
The compounds b) may be used both individually and in combination with one another.
In a preferred embodiment, the compounds b) used are those of which the basic fatty acids are saturated fatty acids containing 12 to 16 and more particularly 12 to 14 carbon atoms. Particularly preferred compounds of this class are the mono- and di-ethanolamides of lauric acid, myristic acid and mixtures of these acids occurring in vegetable raw materials, for example coconut fatty acid. The compounds mentioned are used in particular in technical quality.
Another embodiment is characterized by the additional proviso that the mixture containing components a), b) and c) contains fatty acid amides based on unsaturated fatty acids in at most a quantity which corresponds to 10% by weight, based on the quantity of fatty acid amides b) based on saturated fatty acids.
The compounds b) to be used in accordance with the invention are capable of migration. This means that these compounds are capable of moving during production, for example by extrusion, to the surface of the resulting polyolefin molding. Accordingly, they accumulate at the surface of the plastic matrix or in zones near its surface which Applicants were able to verify by successive removal of surface layers of the order of a few nanometers in thickness and subsequent application of Abscan techniques.
The use of the special fatty acid amides b) mentioned in accordance with the invention ensures that coatings and adhesives are able to adhere to the plastic permanently and without additional pretreatment. Once established, adhesive and/or coating compatibility values remain intact for long periods or sometimes even increase in the event of continued storage. According to the invention, there are basically no restrictions as to the type of adhesives and coating compositions which can be brought into contact with the polyolefins surface-modified in accordance with the invention so that permanent bonding or coating is achieved. Thus, any adhesives known to the expert, especially commercially available adhesives, may be used as the adhesives. So far as coatings are concerned, paints are particularly relevant. Paints are liquids or powder-form solids which are applied in thin layers to surfaces and which form a strong decorative and/or protective film on those surfaces by chemical reaction and/or physical processes. Coatings in the context of the invention also include printing inks because printing inks are applied to substrates to be printed in a binder layer, adhesion to the substrate being imparted by the binder which forms a coating.
The mixture containing components a), b) and c) is used in traditional molding techniques well-known to the expert, such as extrusion, calendering, injection molding, blow molding and the like. In a preferred embodiment of the present invention, the melt of the mixture containing components a), b) and c) comes into contact with oxygen, more especially atmospheric oxygen, in the course of the molding process. In the case of extrusion, for example, this happens when the melt leaves the extruder through the extrusion die. The preferred embodiment mentioned above enables oxidativexe2x80x94optionally catalytically assistedxe2x80x94processes and other secondary reactions to take place. (Atmospheric) oxygen can act on the one hand on the surface itself and, on the other hand, even in the interior of the plasticxe2x80x94especially in zones near the surfacexe2x80x94to which it is capable of diffusing.
The combination of the teaching according to the invention which leads to high adhesive or coating compatibility values with technologies known per se for improving coating or adhesive compatibility on polyolefin surfaces falls within the scope of the teaching according to the invention. Thus, the surfaces of the polyolefins produced in accordance with the invention may also be both mechanically and chemically and/or physically treated. However, this is generally not necessary.
As already mentioned, the compounds b) are used in combination with transition metal compounds c) during the molding of the polyolefins a). The quantity of transition metal compoundxe2x80x94metal content of the transition metal compound based on the polyolefinsxe2x80x94is in the range from 0.01 to 1000 ppm. Basically, there are no particular restrictions as to the nature of the transition metal compounds. In principle, therefore, any transition metal compounds known to the expert may be used for the purposes of the teaching according to the invention. In one embodiment, transition metal salts, preferably salts based on organic acids containing 6 to 22 carbon atoms, are used as the transition metal compounds. In another embodiment, the transition metal compounds are used in a quantity below 5 ppmxe2x80x94metal content of the transition metal compound based on the polyolefins. Another embodiment is characterized by the use of transition metal compounds c) of which the metals are selected from the group consisting of Co, Zr, Fe, Pb, Mn, Ni, Cr, V, Ce, Ti and Sn.
If desired, other compounds known to the expert as catalysts for oxidative processes may be used in addition to the compulsory transition metal compounds mentioned.
In one preferred embodiment, the ratio by weight of the compounds b) to the metal content of the transition metal compounds c) is adjusted to a value of 10:0.1 to 10:10xe2x88x927, preferably to a value of 10:0.02 to 10:10xe2x88x926 and more preferably to a value of 10:0.01 to 10:10xe2x88x925.
According to the invention, the special fatty acid amides b) are used in the course of routine molding processes, such as extrusion, calendering, injection molding, blow molding and the like. It may be desirable to use components a), b) and c) in the form of a mixture prepared in advance. Other typical auxiliaries which have generally been successful in the molding of plastics and which are known to the expert, for example slip agents, antistatic agents, lubricants, release agents, UV stabilizers, antioxidants, fillers, fire retardants, mold release agents, nucleating agents and antiblocking agents, may also be separately made up and added during the final mixing of the end products. The common practice of using the auxiliaries mentioned in a form in which they are already completely or partly present in component a) is also expressly included within the scope of the present invention.
However, it may also be desirable, for example where extrusion is applied, to introduce components b) and/or c) and/or other additives either completely or partly into the polyolefin melt itself in the extruder, so that the mixture of components a), b) and c)xe2x80x94and optionally other auxiliariesxe2x80x94is not present from the outset as a made-up product, but is formed in the extruder itself. A technique such as this is appropriate, for example, when the compounds b) to be added to the polymer melt are present in liquid form and are easier to inject than to make up in advance.
It may even be desirable, although not necessary for obtaining the effect according to the invention, to undertake a conventional corona or plasma treatment after the use of components a) to c) in accordance with the invention.
Basically, any known ethylene- or propylene-based polymers and copolymers may be used as the basic oleophilic polyolefin material.
Mixtures of pure polyolefins with copolymers are also suitable in principle providing the compounds b) retain their ability to migrate in accordance with the invention and hence to collect at the surfaces of solids. Polymers particularly suitable for the purposes of the teaching according to the invention are listed below: poly(ethylenes), such as HDPE (high-density polyethylene), LDPE (low-density polyethylene), VLDPE (very-low-density polyethylene), LLDPE (linear low-density polyethylene), MDPE (medium-density polyethylene), UHMPE (ultra high molecular polyethylene), VPE (crosslinked polyethylene), HPPE (high-pressure polyethylene); isotactic polypropylene; syndiotactic polypropylene; Metallocen-catalyzed polypropylene, high-impact polypropylene, random copolymers based on ethylene and propylene, block copolymers based on ethylene and propylene; EPM (poly[ethylene-co-propylene]); EPDM (poly[ethylene-co-propylene-co-unconjugated diene]).
Other suitable polymers are: poly(styrene); poly(methylstyrene); poly(oxymethylene); Metallocen-catalyzed xcex1-olefin or cycloolefin copolymers, such as norbornene/ethylene copolymers; copolymers containing at least 80% ethylene and/or styrene and less than 20% monomers, such as vinyl acetate, acrylates, methacrylates, acrylic acid, acrylonitrile, vinyl chloride. Examples of such polymers are: poly(ethylene-co-ethyl acrylate), poly(ethylene-co-vinyl acetate), poly(ethylene-co-vinyl chloride), poly(styrene-co-acrylonitrile). Also suitable are graft copolymers and polymer blends, i.e. mixtures of polymers in which the above-mentioned polymers inter alia are present, for example polymer blends based on polyethylene and polypropylene.
Homopolymers and copolymers based on ethylene and propylene are particularly preferred for the purposes of the present invention. In one embodiment of the present invention, therefore, polyethylene on its own is used as the polyolefin; in another embodiment, polypropylene on its own is used as the polyolefin and, in a further embodiment, ethylene/propylene copolymers are used as the polyolefin.
The application of coatings or adhesives to the surface-modified polyolefin-based moldings and films obtained by the process according to the invention may basically be carried out by any of the relevant methods known to the expert.
In one embodiment, polyethylene is used as component a). If it is HDPE (high-density polyethylene), a temperature of 200 to 300xc2x0 C. is preferably adjusted during molding whereas, in the case of HDPE containing carbon black, the molding temperature is preferably adjusted to a value in the range from 250 to 300xc2x0 C. If LDPE (low-density polyethylene) is used, a temperature of 180 to 260xc2x0 C. and more particularly in the range from 200 to 260xc2x0 C. is preferably adjusted during the molding process.
In the case of extrusion processes, the temperatures just mentioned for HDPE and LDPE apply in particular to the temperature of the die.
If the mixture of components a), b) and c) is molded by extrusion, the polyolefin molding is cooled by at most 50xc2x0 C., preferably in 0.1 to 5.0 seconds, immediately after leaving the die. Accordingly, this temperature difference of 50xc2x0 C.xe2x80x94hereinafter also referred to as xcex94T50xe2x80x94is governed by the following equation:
xcex94T50=Tdiexe2x88x92Tpolyolefin surface
where Tdie is the temperature of the extrusion die while Tpolyolefin surface is the surface temperature of the extruded polyolefin molding as measured without any contact, for example using relevant known infrared techniques (for example with a Chino xe2x80x9cIR-TA/Handy 1000xe2x80x9d infrared thermometer).
In one particularly preferred embodiment, the polyolefin molding is cooled by at most 50xc2x0 C. in 1.0 to 5.0 seconds and more particularly in 1.7 to 5.0 seconds immediately after leaving the extrusion die.
Assuming that the polyolefin molding moves at a constant speed after leaving the extrusion die, the time scale mentioned can easily be converted into a distance scale using the known equation v=s/t (speed=distance divided by time) which can be transformed to s=v*t (distance=speed multiplied by time) from which it can be seen that distance s (i.e. distance from the extrusion die) and time t are proportional to one another. By definition, the zero point of the distance scale is situated immediately at the exit point of the die.
The polyolefin moldings obtainable using the fatty acid amides b), more particularly the granules obtainable by extrusion, may be used as so-called master batches in the processing of bulk plastics.
The present invention also relates to a process for the production of bonded and/or coated polyolefin-based moldings, fibers and films, in which a mixture containing
a) predominantly one or more polyolefins,
b) 0.01 to 20% by weightxe2x80x94based on the polyolefinsxe2x80x94of one or more fatty acid amides and
c) 0.01 to 1000 ppm of one or more transition metal compoundsxe2x80x94metal content of the transition metal compounds, based on the polyolefinsxe2x80x94is subjected in known manner to molding by extrusion, calendering, injection molding, blow molding and the like at temperatures of 180 to 330xc2x0 C. and the resulting polyolefin-based moldings, fibers and films with improved adhesive and/or coating compatibility are subsequently contacted in the usual way with an adhesive and/or a coating composition, characterized in that the fatty acid amides b) are selected from the class of compounds corresponding to general formula (I): 
in which R1 is a saturated alkyl group containing 5 to 21 carbon atoms, R2 and R3 independently of one another are hydrogen or alkyl groups containing 1 to 18 carbon atoms which may each be substituted by up to 6 OH groups, NH2 groups or C1-10 alkyl groups and in which up to three methylene groups which are not immediately adjacent one another may be replaced by oxygen, with the proviso that R1 and R2 cannot both be hydrogen and the additional proviso that the mixture containing components a), b) and c) contains fatty acid amides based on unsaturated fatty acids at most in a quantity which corresponds to 40% by weight, based on the quantity of fatty acid amides b) based on saturated fatty acids.